Healthy Fat Patients Have Lower Risk of Mortality, CVD Morbidity

In fact, researchers showed that the risk of all-cause mortality, cardiovascular morality, and cardiovascular events was equivalent among metabolically healthy but obese individuals with high levels of cardiorespiratory fitness and normal-weight individuals.

"Once fitness is duly accounted for and an accurate measure of adiposity is used, the metabolically healthy but obese phenotype is a benign condition, with a better prognosis (30% to 50% lower risk) for mortality and morbidity than metabolically abnormal obese people," say Dr. Francisco Ortega (Karolinksa Institute, Stockholm, Sweden) and colleagues in the report. "Interestingly, no difference in the prognosis is observed between metabolically healthy but obese individuals and metabolically healthy normal-fat individuals once fitness is accounted for, suggesting a key role of fitness in these associations."

In their paper, in which the researchers label the metabolically healthy but obese subjects an "intriguing" population, they differentiate between obese but metabolically healthy and metabolically obese but normal-weight individuals. The "skinny-fat" patients have a normal body-mass index (BMI) but tend to be insulin resistant, predisposed to type 2 diabetes, hypertriglyceridemia, and premature coronary heart disease. In metabolically healthy but obese patients, cardiorespiratory fitness is believed to play a role in keeping fatter patients at lower risk for premature cardiovascular disease and partially explains why they have a healthier cardiovascular risk profile.

The latest study of the "fat-and-fit" phenomenon included an assessment of fitness with a maximal exercise test on a treadmill and an assessment of body-fat percentage of 43,265 adults participating in the Aerobics Center Longitudinal Study (ACLS). Individuals were considered metabolically healthy if they had zero or one component of the metabolic syndrome. Based on the BMI and body-fat–percentage criteria, 13.1% and 29.7% of subjects were considered obese. Of these obese individuals, 30.8% of the BMI-based obese subjects and 46.3% of the body-fat-percentage–based obese subjects were metabolically healthy. The median follow-up period for assessing mortality outcomes was 14.3 years and 7.9 years for nonfatal cardiovascular disease outcomes.

Overall, the metabolically healthy but obese individuals had higher baseline fitness levels than metabolically abnormal obese subjects (in both definitions of obesity). All-cause mortality, cardiovascular mortality, and nonfatal cardiovascular events were all statistically lower among the metabolically healthy but obese individuals when compared with metabolically abnormal and obese subjects. When compared with healthy-weight individuals, the mortality and nonfatal cardiovascular events were similar.

In an editorial accompanying the study, Drs. Stephan von Haehling, Oliver Hartmann, and Stefan Anker (Charité Medical School, Berlin, Germany) say they were surprised that the researchers selected the metabolically healthy but obese individuals as the reference group, noting that they would have chosen the healthy/nonobese patients as the reference group, as this cohort included more than three times as many patients than the other two groups combined. Methodology aside, the editorialists also would like to have seen an analysis that examined a range of obese/body-fat measurements to see whether there was a graded or linear relationship between obesity/body-fat and mortality and cardiovascular morbidity.

On the whole, however, they conclude that, "Obesity may carry benefit up to a certain degree, and it should be recognized that obesity is not necessarily associated with abnormal metabolic function."

Published online September 5, 2012 in the European Heart Journal

Ortega FB, Lee DC, Katzmarzyk PT, et al. The intriguing metabolically healthy but obese phenotype: cardiovascular prognosis and role of fitness. Eur Heart J 2012; DOI:10.1093/eurheartj/ehs174. Available at: http://eurheartj.oxfordjournals.org. 22947612

von Haehling S, Hartmann O, Anker SD. Does obesity make it better or worse? Insight into cardiovascular illnesses. Eur Heart J 2012; DOI:10.1093/eurheartj/ehs237. Available at: http://eurheartj.oxfordjournals.org. 22947611